Carnivora
Carnivora is a diverse n that includes over 280 species of s. Its members are formally referred to as carnivorans, whereas the word " " (often popularly applied to members of this group) can refer to any meat-eating organism. Carnivorans are the most diverse in size of any mammalian order, ranging from the (Mustela nivalis), at as little as 25 g (0.88 oz) and 11 cm (4.3 in), to the (Ursus maritimus), which can weigh up to 1,000 kg (2,200 lb), to the (Mirounga leonina), whose adult males weigh up to 5,000 kg (11,000 lb) and measure up to 6.7 m (22 ft) in length. Carnivorans have teeth and claws adapted for catching and eating other animals. Many and are s, giving them an advantage over larger prey. Some carnivorans, such as and s, for their nutrition. Others, such as s and s, are more , depending on the habitat. The is largely a , but also feeds on , and s. The polar bear subsists mainly on seals. Carnivorans evolved in North America out of members of the family (miacids) about 42 million years ago. They soon split into cat-like and dog-like forms ( and ). Their molecular phylogeny shows the extant Carnivora are a group, the of the . Distinguishing features , showing the sharp teeth and claws characteristic of carnivorans}} Most carnivorans are ; they usually have strong, sharp s, typically with five, but never fewer than four, toes on each foot, and well-developed, prominent , teeth ( s, and ) that generally have cutting edges. The last premolar of the upper jaw and first molar of the lower are termed the teeth. These blade-like teeth occlude (close) with a scissor-like action for and meat. Carnassials are most highly developed in the and the least developed in the . Carnivorans have six s and two canines in each jaw. The only two exceptions to this are the (Enhydra lutris), which has four incisors in the lower jaw, and the (Melursus ursinus), which has four incisors in the upper jaw. The number of molars and premolars is variable between carnivoran species, but all teeth are deeply rooted and are . Incisors are retained by carnivorans and the third incisor is commonly large and sharp (canine-like). Carnivorans have either four or five digits on each foot, with the first digit on the forepaws, also known as the , being in most species and absent in some. The superfamily (or suborder ) – (wolves, dogs and foxes), (skunks and stink badgers), (weasels, badgers, and otters), (raccoons), (bears), (red panda), (eared seals), (walrus), and (earless seals) (the last three families formerly classified in the superfamily ) and the extinct family (bear-dogs) – are characterized by having nonchambered or partially chambered , nonretractable claws, and a well-developed . Most species are rather plain in coloration, lacking the flashy spotted or rosetted coats like many species of and have. This is because Canoidea tend to range in the temperate and subarctic , although Mustelidae and Procyonidae have a few tropical species. Most are terrestrial, although a few species, like , are arboreal. All families except the and a few species of are . Diet is varied and most tend to be omnivorous to some degree, and thus the carnassial teeth are less specialized. Canoidea have more premolars and molars in an elongated skull. The superfamily (or suborder )– (cats), (Asiatic linsangs), (mongooses), (hyenas), (civets), and (Malagasy carnivorans), as well as the extinct family (paleofelids) – often have spotted, rosetted or striped coats, and tend to be more brilliantly colored than their Canoidean counterparts. This is because these species tend to range in tropical habitats, although a few species do inhabit temperate and subarctic habitats. Many are arboreal or semiarboreal, and the majority are digitigrade. Diet tends to be more strictly carnivorous, especially in the family Felidae. They have fewer teeth and shorter skulls, with much more specialized carnassials meant for shearing meat. Feliformia claws are often retractile, or rarely, semiretractile. The terminal phalanx, with the claw attached, folds back in the forefoot into a sheath by the outer side of the middle phalanx of the digit, and is retained in this position when at rest by a strong elastic ligament. In the hindfoot, the terminal joint or phalanx is retracted on to the top, and not the side of the middle phalanx. Deep flexor muscles straighten the terminal phalanges, so the claws protrude from their sheaths, and the soft "velvety" paw becomes suddenly converted into a formidable weapon. The habitual retraction of the claws preserves their points from wear. The superfamily (walruses, seals, and sea lions), now considered to be part of Caniformia, are medium to large (to 6.5 m) aquatic mammals. Being homeothermic (warm-blooded) marine mammals, pinnipeds need a low surface area to body mass ratio. Otherwise, they would suffer from excessive heat loss due to water's high capacity for heat conduction. The body is usually insulated with a thick layer of fat called and typically covered with hair. The digits are not separate, but connected by a thick web that forms flippers for swimming; thus, the forelimbs and hindlimbs are transformed into paddles. This enables them to dive to extreme depths (600 m for the ). They can remain underwater for long periods of time, sometimes an hour or more, but most dives are usually short. The facial region of skull is relatively small, with very small or lacking, and the are well developed. The molariform teeth are mostly and the canines are well developed. The tail is very short or absent, the ears are small or absent as well, and the external are hidden in slits or depressions in the body. Phylogenetic tree |1= ' |1= ' |1= ' |1= ' |2=' ' (hyaenas) |3=†' ' }} |2= ' (mongoose) |2=' ' (Malagasy mongooses) }} }} |2=' ' (viverrids) }} |label2= ' ' |2= ' (Asiatic linsang) |2= ' |2=' ' (cats) }} }} }} |2=' ' (African palm civet) }} |2=†' ' (false saber-toothed cats) }} |label2= ' ' |2= ' ("bear-dogs") |2= '' |label2= |2= ' (canids) |label2= |2= |1= ' ("dog-bears") |2=' ' (bears) }} |2= |1= |1= ' (eared seals) |2=' ' (walruses) }} |2=' ' (earless seals) }} |2=†' ' }} |label2= |2= ' |2= ' (skunks) |2= ' (raccoons) |2=' ' (mustelids) }} }} }} }} }} }} }} }} }} }} References Category:Tree of life